President Barack Obama’s claim last week that California’s worst drought in a century is linked to global warming due to greenhouse gas emissions has been disputed by some scientists.

"I’m pretty sure the severity of this thing is due to natural variability," Richard Seager, a climate scientist who studies water issues at the Lamont-Doherty Earth Observatory of Columbia University in New York, told The New York Times.

Seager has based his claim that climate change has played little role in causing the drought on recent computer projections suggest that as the world warms, California should get wetter not drier in the winter, according to The Times.

The drought, which has lasted three years, has made 2013 the driest year in California since records were first kept 119 years ago. But The Times says there’s no concrete evidence to support theories that a warming planet has caused California’s drought leading to a water shortage.

Scientists admit that temperatures in California have been increasing over the recent years, and the temperatures have been far higher in recent months, 10 to 15 degrees above normal, than during a previous drought in the region in 1976-1977.

The result has been that any moisture that state does receive is evaporating more quickly, worsening the effects of the drought, particularly on agriculture.

Michael Anderson, the California state climatologist, said, "We are going through a pattern we’ve seen before, but we’re doing it in a warmer environment.”

Las week, while on a tour of central California, Obama announced $160 million in federal financial aid to the state, including $100 million in the farm bill he’d previously signed into law for programs that cover the loss of livestock.

White House science adviser John Holdren stated last week that, ultimately, climate change is the reason behind California’s water shortage, even though "no single episode of extreme weather" can be blamed on global warming.

He said, "The global climate has now been so extensively impacted by the human-caused buildup of greenhouse gases that weather practically everywhere is being influenced by climate change."

Seager said that southwestern states have suffered drought conditions in some form for 15 years, and warmer climates have resulted in winter precipitation tending to fall as rain rather than snow. With less snow melting during the spring, these states face a lack of water during the hot summer months.

"It all adds up across the Southwest to an increasingly stressed water system," he said. "That’s what they might as well get ready for."

Major reservoirs throughout California only have half the water they need to at this time of year, The Times added. "I think the situation is still pretty severe," said Prof. Alex Hall, who studies climate at the University of California, Los Angeles.